Some properties of saliva such as buffer capacity, secretion rate, anti-bacterial activities and effects on bacterial colonization are suggested to be of importance for the development of dental caries. Such properties would be dependent upon the biosynthesis and secretion of substances from the salivary glands. The aim of this study is to investigate the effect of malnutrition on the composition of whole saliva and on incidence of caries in rats fed sucrose. Twenty rats were fed nutritionally adequate diets by gastric intubation. Ten of these received a supplement of sucrose and 10 of starch. Another 20 rats were fed the basic diet diluted with an equal volume of water; ten were supplemented with sucrose and with starch. The supplements are distributed 17 times daily. Caries will be scored and the effect of the reduced diet on some antibacterial systems in saliva will be measured.